It has cooled down again. For many aircraft users who have to wear gloves to keep warm, this is bound to bring a lot of inconvenience to playing with computers.There is no pressure for the powerful and powerful, glove wearing machine like the Lumia 920. For those who use the Lumia 920, you can also buy touch screen gloves andLove to play computer gamesPreviously introducedAnyGlove DropsTo solve this problem.However, have you ever thought about why you need to wear special touch screen gloves to play with computers?
First, let's start with the touch screen.There are two common touch screens. One is resistance screen, which realizes touch induction through the current change generated by screen pressure induction. The resistance screen does not have the problem of being unable to operate with gloves. The problem is the capacitive screen used by most models. Its principle is that when the capacitance screen works, an AC electric field is formed in the conductive interlayer. When the human body touches the screen,A capacitance will be formed between the finger and the conductor layer and discharge will occur. A certain amount of charge will be transferred to the human body, which will lead to the change of the electrode voltage at the edge of the screen. The accurate position of the touch can be calculated according to this.Wearing gloves is equivalent to adding a layer of insulating material, making the capacitive screen unable to react to it.
Children's shoes of science, the following is the moment to check whether you have returned your middle school textbook to the teacher:
[Capacitor]: It is a device for storing electric charge, which is composed of two conductors (two polar plates) that are insulated from each other (or filled with dielectric) and closely separated.The simplest capacitor is called parallel plate capacitor, as shown in the figure below:
If you are still impressed with physics in middle school, you may remember that the ratio of the charge quantity Q carried by the capacitor to the potential difference U between the two plates of the capacitor is called the capacitance of the capacitor, namely:
C=Q/U。
This formula is called the definition of capacitance. It tells us that the charge quantity Q of a given capacitor is proportional to the potential difference U between the two plates of the capacitor, and the ratio is a constant.It was previously reported thatThe reason why the screen is more sensitive is that Lumia 920 increases the voltage of the electrode, resulting in an increase in the number of charges in the mesh electric field in the touch screen. However, from the above formula, the capacitance of the capacitor is not related to Q and U, but is determined by the structure of the capacitor itself.Why is the touch screen of Lumia 920 more sensitive?Let's look at the second determinant for parallel plate capacitors (where k is the electrostatic force constant):
This formula explains the factors that affect the capacitance of parallel plate capacitor, that is, the area S between the two plates, the distance D between the two plates, and the dielectric constant ε r.The larger the positive area between the two plates, the smaller the spacing, and the larger the dielectric constant, the larger the value of capacitance C, and the more sensitive the capacitive screen.
We can also analyze these three factors in detail:
1. Opposite area S
As can be seen from the following video, if we touch the iPad only with a small area of finger tip after putting on the business card (changing the dielectric constant and reducing the sensitivity), the touch screen will not respond;However, if we increase the area of fingers and touch screen, the value of C changes, and the capacitive screen can also respond accordingly according to our operation;
2. Spacing D
The reason why Lumia 920 is more sensitive is that the distance between the fingers and the electric field of the conductor is reduced: the ultra sensitive touch screen adopted by Lumia 920 integrates the display screen and the sensor, which makes the thickness of the ultra sensitive touch screen thinner than the ordinary touch screen by a full 1mm (as shown in the following figure).At the same time, the position of the sensor and the transmitter that used to be above the display screen has changed. The transmitter has become the back of the display, and the sensor has become the front of the display. This adjustment has improved the signal-to-noise ratio, enabling the sensor to capture weaker touch signals;
3. Dielectric constant ε r
Different dielectrics have different dielectric constants ε r.For example, the ε r of air is about 1, that of kerosene is 2, that of ceramics is 6, and that of mica is 81.(By the way, the dielectric constant is used to describe the insulation, while the metal is a conductor, and the current can pass through but is difficult to stay. There are special papers on the dielectric constant of metal, which will not be discussed here.)
The main reason why ordinary gloves cannot make the touch screen react is that gloves are insulating materials with low dielectric parameters. The so-called touch screen gloves actually implant very thin metal wires at the fingertips of gloves, thus enhancing the ability to conduct electric charges;Similarly, the AnyGlove drop mentioned earlier is essentially a dielectric. By changing the dielectric parameter of the "coupling capacitance" formed by the human body and the touch screen, the capacitance C value becomes larger, so that we can operate with gloves.
After knowing the principle of touch screen gloves, Aigo Machine will also try to make DIY touch screen gloves. Please pay attention to the following articles.
